Radders Posted August 30, 2011 Share Posted August 30, 2011 I need some advice on alternator wiring. On the back of the alternator there are three pins which the nylon plug with three wires plugs onto. My nylon plug has long gone, but there are only two wires so one pin is left free. (The middle one I think?)The question is, should there definitely be three wires? If so, where do they go? The reason I'm askling is is that I seem to be having an issue with alternators. I have purchased two brand new ones now (65 amp) only for the ignition light to glow when I have lot of electrical items switched on. Is this something to do with my missing wire, or am I just being seriously unlucky with alternators??? :-/ Link to comment Share on other sites More sharing options...
beefertoo Posted August 30, 2011 Share Posted August 30, 2011 assuming lucas, there is two big connectors and 1 small. the 2 big ones go directly to battery and small 1 to ign light.normal on a lower output to have just 1 big connected but would suggest running another wire to battery if upgrading.btw if you take the plastic cover off you'll see the big connectors are joined anyway.craig Link to comment Share on other sites More sharing options...
Richard B Posted August 30, 2011 Share Posted August 30, 2011 391 wrote:My nylon plug has long gone, but there are only two wires so one pin is left free. (The middle one I think?)The question is, should there definitely be three wires? If so, where do they go? Is this something to do with my missing wire, or am I just being seriously unlucky with alternators??? :-/Well.......The two large terminals are only rated at 35 amp (each), they are common on the alternator. Also do you still have the OE ammeter fitted?What I did on my MkI PI is run a second (heavy) wire that terminal on the alternator direct to the + on the battery and bypassing the ammeter. Link to comment Share on other sites More sharing options...
thescrapman Posted August 30, 2011 Share Posted August 30, 2011 Don't forget it was a dynamo car originally, so teh butchers before us may have messed up the removal of teh control box, should not have though as it worked fine with a 65A alternator for about 5000 miles. (alternator then packed up on 10CR 2007 and cooked my battery, but that is another story)Check the wiring to the dash light is OK.You could also experiment and run a wire to a new bulb and see if that glows as well.The Lucas alternators need the bulb working to start charging.I left it with the ammeter still connected, should show 2-3 amps charging all teh time once battery is charged, that is the load from the coil etc I think.If as you turn all teh lights etc on with it at about 1000rpm the ammeter doesn't go into discharge it is working fine.Also make sure you are getting 14 odd volts.CheersColin Link to comment Share on other sites More sharing options...
Richard B Posted August 30, 2011 Share Posted August 30, 2011 thescrapman wrote:Don't forget it was a dynamo car originally, so teh butchers before us may have messed up the removal of teh control box, That might have been me.... :B Link to comment Share on other sites More sharing options...
Radders Posted August 30, 2011 Author Share Posted August 30, 2011 Richard_B wrote:That might have been me.... :BMaybe not Richard, this is Gertie.........not the yellow beast. :) Link to comment Share on other sites More sharing options...
Richard B Posted August 30, 2011 Share Posted August 30, 2011 Phewww! (pray) Link to comment Share on other sites More sharing options...
Alex Posted August 30, 2011 Share Posted August 30, 2011 Richard_B wrote:Phewww! (pray)one you didnt break ;D Link to comment Share on other sites More sharing options...
junkuser Posted August 31, 2011 Share Posted August 31, 2011 Indicator lamp can glow dimly due to higher resistance between battery and ignition side of lamp compared to the D+ side giving a voltage drop across the lamp.A volt meter is more useful with an alternator than an ammeter as it will show any drop off of voltage as soon as the alternator or wiring start to give troubles with a decent change in needle deflection. If you use an ammeter designed to handle, say, 65Amps, then the needle deflection during normal running is so small as to be meaningless in meters of the quality made for automotive use as the full sweep of 130 Amps is covered in 60 degrees of arc or so. Link to comment Share on other sites More sharing options...
Radders Posted August 31, 2011 Author Share Posted August 31, 2011 Hopefully now resolved. Test drive to the Essex meet tonight. (well, on the way home when it's dark!)If successful will announce said remedy tomorrow. :) Link to comment Share on other sites More sharing options...
Radders Posted September 1, 2011 Author Share Posted September 1, 2011 Now fully cured! As suggested, an additional wire was fitted on the 'empty' pin on the alternator and run to the + side of the battery. We noticed that before we fitted the extra wire the alternator would pump 14 volts into the battery, but this dropped lower each time you switched something on. By the time we had the headlights, spotlights, wipers & heater on it was down to just under 13 volts. With the extra wire added, this stayed at 14 volts no matter what was switched on.The ignition light doesn't glow red anymore either, so job jobbed! A bit more peace of mind for the 10CR. ;)Thanks for the advice! :) Link to comment Share on other sites More sharing options...
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